Yeah, I had reached that conclusion too.
I was talking to him and the order has expanded a bit:
We need:
2 full PC's equipped with good graphics cards and processors.
1 good graphics card.

They are going into an architectural firm which uses them for CAD Design and 3D image rendering.

My dad uses two screens and loves to keep a horde of processes running. Seeing as the Q6600 is now cheap it seems like a natural choice.

BTW The office is in Sothern California so: a) if you want to find relevant pricing information use US dollars, so far I have only chosen parts of Newegg.com but there are a lot of other good websites, and b) good cooling and upgradability are important.

an 8600 Will be fine for use of that. the q6600 would be good for rendering things, cause its real cheap right now. As for ram, you want the timings to be higher aka 5-5-5-15. I do not remember why, i just know that 4-4-4-12 is better for gaming, and 5-5-5-15 is better for photoshop and rendering programs

Do not use a Geforce or a Radeon, PLEASE. For CAD, use a Quadro or FireGL. The PNY Quadro FX 570 is a great entry level CAD or 3D design dual head graphics card, and is $200. Match that to a decent Core2Duo or Quad (intel or AMD is fine), and 4GB RAM. Be sure to use XP Pro.

Do not use a Geforce or a Radeon, PLEASE. For CAD, use a Quadro or FireGL. The PNY Quadro FX 570 is a great entry level CAD or 3D design dual head graphics card, and is $200. Match that to a decent Core2Duo or Quad (intel or AMD is fine), and 4GB RAM. Be sure to use XP Pro.